Process for producing wort for fermented malt drinks

ABSTRACT

The present invention provides a process for producing a wort with reduced content of a stale flavor-causing substance for the production of fermented malt beverages such as beer and the like in which generation of a stale flavor is suppressed, and it also provides fermented malt beverages in which generation of a stale flavor is suppressed such as beer and the like, that are produced by using wort with low content of a stale flavor-causing substance obtained by this process for producing. The second wort with reduced content of a stale flavor-causing substance is obtained with trans-2-nonenal potential (NP) as an indicator in the wort separation of a prepared wort in the production of fermented malt beverages by; eluting the substance with hot water for the sparging containing calcium salts and organic acids; eluting the substance with hot water for the sparging which can lower the temperature in the spent grains to 70° C. or under; or using the second wort again during mashing process. Fermented malt beverages with suppressed generation of a stale flavor-causing substance is produced by using wort in which NP in the whole wort is reduced by at least 1 ppb in terms of sugar content 11° p.

TECHNICAL FIELD

[0001] The present invention relates to a process for producing wort forthe use of production of fermented malt beverages such as beer and thelike, in which the generation of a stale flavor is suppressed, and moreparticularly to the process for producing wort whose content of a staleflavor-causing substance is reduced during the wort production steps forproducing fermented malt beverages such as beer and the like.

BACKGROUND ARTS

[0002] In fermented malt beverages such as beer and the like with maltas a raw material, chemical reactions such as oxidation and the like areaccelerated due to the passage of time, the rise in temperature, and soon, thereby deterioration of the products is progressed. Products oncedeteriorated suffer damage to their original taste and flavor containedin fermented malt beverages and their quality is deteriorated. In orderto prevent such quality deterioration in fermented malt beverages,various attempts have been made as shown below.

[0003] The publication of Japanese Laid-Open Patent ApplicationNo.1993-137555 describes a process referring to the use of malt whereinlipid is removed in advance from the beer malt by sub-critical orsuper-critical carbon dioxide, as a process for producing beer with theuse of malt from which lipid, which damages quality, has beenselectively and efficiently removed without affecting enzymes in themalt, in beer or in the beer production steps. According to thedescription, the filtering efficiency, foam-lastingness and flavorstability will improve, yet this process requires a step of treating rawmaterials with super-critical carbon dioxide, which leads to theincrease in the production cost.

[0004] The publication of Japanese Laid-Open Patent ApplicationNo.2000-4867 describes as a production process for malt alcoholicbeverages with high flavor lastingness and a management method forcontrolling the generation of a substance which indicates the flavorlastingness in an intermediate sample in the production process for maltalcoholic beverages including the steps of: selection of raw materialsincluding malt; wort production; fermentation; maturation; filtration;and container filling. The description continues that5-hydroxymethylfurfural (5-HMF) or its precursor is selected as anindicator for flavor lastingness and malt alcoholic beverages with highflavor lastingness can be produced by successfully suppressing thisindicator substance in the course of production. It further disclosesspecific examples including a method of suppressing 5-HMF generation byadding an amino acid which has a thiol group and a method of giving theanti-oxidation property to the wort by the addition of catechin. But inorder to raise the effectiveness of suppressing 5-HMF generation,multiple execution of the treatment process will be required and thesteps are anticipated to become complicated.

[0005] The following mechanisms have been presented with regard to thegeneration of a beer stale flavor which deteriorates the taste offermented malt beverages such as beer and the like. They are: Maillardreaction and Strecker degradation of amino acids; autoxidation of fattyacids and enzymatic oxidation of lipids; oxidative degradation of abitter substance in the hop, oxidation of higher alcohols bymelanoidines, oxidation of the unsaturated hydroxyfatty acid or alcoholscatalyzed with a metal ion (Cu, in particular); and oxidation of ahigher alcohol. These or some among these are thought to be involved inthe generation of a stale flavor (Hideo MIYAJI, “Beer BrewingTechnology”, Shokuhin Sangyo Shimbunsha, Co., Ltd., published on Dec.28, 1998; pp.418-424).

[0006] On the other hand, a stale flavor itself has been studied.Trans-2-nonenal is exemplified as one of the substances causing a staleflavor. One of the generation pathways for this substance is as follows:a trans-2-nonenal precursor (a hydroxide derivative), derived from lipidor the fatty acid in the raw material, is generated upon both enzymaticand non-enzymatic oxidations in the course of wort preparation, whichfurther leads to the generation of trans-2-nonenal through the oxidativedegradation. It is argued that, even though the above-mentionedprecursor is removed to a high degree in the courses of fermentation andmaturation, the precursor transfers on to the finished beer and then, bythe later oxidation, trans-2-nonenal generates in the beer and the like.It is, however, rather thought that trans-2-nonenal produced in the wortforms Schiff bases with primary amines, such as amino acids, in the wortand that some of the Schiff bases are passed on to the beer and thelike, where trans-2-nonenal is freed from Schiff bases depending on thetemperature- or pH-condition, although many of them are removed in thecourses of fermentation and maturation (Lermusieau et al., J. Am. Soc.Brew. Chem. 57, 1999, p29-33).

[0007] The subject of the present invention is to provide a process forproducing wort with reduced content of a stale flavor-causing substancefor the purpose of producing fermented malt beverages such as beer andthe like in which a stale flavor generation is suppressed, and toprovide fermented malt beverages such as beer and the like in which astale flavor generation is suppressed, that are produced by using wortwith low content of a stale flavor-causing substance obtained by thisproduction process.

[0008] In the course of studying the suppression of the generation of astale flavor in beer, the present inventor focused on trans-2-nonenalamong various substances causing a stale flavor and analyzed in detailsthe behavior of a trans-2-nonenal precursor in the beer productionsteps. The present inventor then found out that in order to estimate thelevels of trans-2-nonenal in the beer products generated during storage,it is important to grasp prosperity and decay of a trans-2-nonenalprecursor in the wort, and that the trans-2-nonenal level, in the wortadjusted to a certain pH and boiled for a certain time, namelytrans-2-nonenal potential (hereinafter NP), serves as an effectiveindicator for a stale flavor generated in the beer products. Inaddition, the present inventor found out that sugar content in thesparged wort decreases gradually since the last extract is washed out ofthe spent grains, whereas NP content holds a high level withoutcorrelating to the decrease in sugar content during sparging. Thepresent invention has come to the completion based on these findings.

DISCLOSURE OF THE INVENTION

[0009] The present invention relates to: a process for producing wortfor fermented malt beverages wherein a reducing treatment is performedfor a stale flavor-causing substance in the second wort in the mashseparation process in course of the production of fermented maltbeverages, to obtain the second wort with reduced content of a staleflavor-causing substance (claim 1); the process for producing wort forfermented malt beverages according to claim 1, wherein the reducingtreatment of a stale flavor-causing substance is performed with thetrans-2-nonenal potential as an indicator (claim 2); the process forproducing wort for fermented malt beverages according to claim 2,wherein the reducing treatment of a stale flavor-causing substance inthe second wort is performed so that the trans-2-nonenal potential inthe whole wort from mash separation process is reduced by at least 1 ppbin terms of sugar content 11° p (claim 3); the process for producingwort for fermented malt beverages according to any one of claims 1-3,wherein the reducing treatment of a stale flavor-causing substance is asuppressing treatment of the elution of a stale flavor-causing substancefrom the spent grains into the second wort in sparging step which is atreatment to restrict the carry-over of a stale flavor-causing substanceinto the second wort (claim 4); the process for producing wort forfermented malt beverages according to claim 4, wherein the treatment torestrict the carry-over of a stale flavor-causing substance into thesecond wort is a treatment to suppress the elution of a staleflavor-causing substance from the spent grains into the second wort insparging step (claim 5); the process for producing wort for fermentedmalt beverages according to claim 5, wherein the treatment to suppressthe elution of a stale flavor-causing substance is a treatment using hotwater for the sparging which contains calcium salts and organic acids(claim 6); the process for producing wort for fermented malt beveragesaccording to claim 5, wherein the treatment to suppress the elution of astale flavor-causing substance is a treatment using hot water for thesparging which can lower the temperature in the spent grains layer to70° C. or under (claim 7); the process for producing wort for fermentedmalt beverages according to claim 4, wherein the treatment to restrictthe carry-over of a stale flavor-causing substance into the second wortis a treatment to control the supply of hot water for the sparging sothat the sparging is completed with sugar content of the second wort notranging below 3° p (claim 8); the process for producing wort forfermented malt beverages according to claim 4, wherein the treatment torestrict the carry-over of a stale flavor-causing substance into thesecond wort is a treatment to restrict the elution of a staleflavor-causing substance by using the second wort again during mashingprocess (claim 9); the process for producing wort for fermented maltbeverages according to claim 9, wherein the elution of a staleflavor-causing substance is restricted by using mashing-in water, a partof which is replaced with the second wort (claim 10); the process forproducing wort for fermented malt beverages according to any one ofclaims 1-3, wherein the reducing treatment of a stale flavor-causingsubstance is a removing or reducing treatment of a stale flavor-causingsubstance in the second wort (claim 11); the process for producing wortfor fermented malt beverages according to claim 11, wherein the removingor reducing treatment of a stale flavor-causing substance in the secondwort is a removing or reducing treatment in which a part or a whole ofthe second wort is made to contact the activated carbon (claim 12); anda fermented malt beverage with suppressed generation of a stale flavorwhich is obtained through the fermentation step from the wort producedby the process for producing wort for fermented malt beverages accordingto any one of claims 1-12 (claim 13).

BRIEF DESCRIPTION OF DRAWINGS

[0010]FIG. 1 shows the time-course change of sugar content and NP of thesecond wort run-off in the mash separation (lautering).

[0011]FIG. 2 shows the time-course change of sugar content and NP of thewort run-off in the mash separation (lautering).

BEST MODE OF CARRYING OUT THE INVENTION

[0012] The production steps of fermented malt beverage such as beer andthe like are roughly classified into: malt production process, wortproduction process (mashing and wort boiling accompanied with hopaddition), beer production process (fermentation and maturation). Themash separation step after the above described mashing step comprises:draining off of the wort from the spent grains (called in general thefirst wort) containing the extract concentration of 16-20%, while theunsoluble part of the mash, spent grains, form the filter material; andeluting thereafter the extract content remaining in the spent grains bywashing out (sparging) with hot water of approximately 80° C. to obtainthe wort run-off with the extract content of approximately up to 1%(called in general the second wort). Hops are added to the mixture ofboth of the worts, which the mixture is then boiled in the subsequentwort boiling step. Accordingly, “the second wort” is the thiner wortrunning off when the spent grains are sparged after “the first wort” hasrun off, and “the whole wort” means the combined wort of the first andthe second running off. Further, the term “wort” used in the phrase“wort for fermented malt beverages” means wort prepared from theforegoing types of wort.

[0013] There is no specific limitation as to a process for producingwort for fermented malt beverages of the present invention as long asthe process for producing wort includes a reducing treatment of a staleflavor-causing substance in the second wort, in the mash separation inthe production of fermented malt beverages, and as long as it enables toobtain the second wort with reduced content of a stale flavor-causingsubstance. Specific examples for the above mentioned fermented maltbeverages are, beer of various kinds such as top-fermented beer,bottom-fermented beer, and the like, as well as “HAPPOSHU”, a fermentedmalt beverage with lower ratio of malt used than in beer. Although astale flavor-causing substance as mentioned above is not particularlylimited, trans-2-nonenal and a substance which may turn intotrans-2-nonenal, i.e. NP component, can be preferably exemplified. Also,a reducing treatment of a stale flavor-causing substance, in the abovesecond wort, can be exemplified by a treatment performed using NP as anindicator. NP level can be determined, for instance, as an amount oftrans-2-nonenal which is yielded after a certain amount (one fifth ofthe buffer) of wort is added to the acetic buffer adjusted to pH 4.0 andis heat-treated for two hours at 100° C.

[0014] With this NP as an indicator, in other words, with thedetermination of NP content in a given step for producing fermented maltbeverages, fermented malt beverages with suppressed generation of astale flavor can be produced by performing a reducing treatment of NPcontent in the second wort. For example, NP content in the whole wortwhere sugar content is adjusted to 11° p (plateau) usually rangesapproximately between 7-10 ppb, although it depends on the types ofbeer. The production of fermented malt beverages with suppressedgeneration of a stale flavor substantially becomes possible by reducingthe NP content in the whole wort at least by 1 ppb.

[0015] There is no specific limitation as to a treatment process toobtain the second wort in which the content of a stale flavor-causingsubstance such as NP component and the like is reduced, for instance, sothat NP content is reduced at least by 1 ppb in the whole wort with itssugar content adjusted to 11° p. Some illustrations are a treatmentprocess in which carry-over of a stale flavor-causing substance into thesecond wort is restricted, for instance, by suppressing its elution fromthe spent grains in the sparging step for the second wort, and atreatment process in which a stale flavor-causing substance is removedor reduced in the second wort. These treatment processes can beperformed either alone or combined. By performing these treatmentprocesses, content of a stale flavor-causing substance such as NPcomponent or the like in the second wort can be reduced, finally theproduction of fermented malt beverages with suppressed generation of astale flavor can be achieved.

[0016] As a treatment process to restrict the carry-over of a staleflavor-causing substance into the second wort, a process can beexemplified in which the elution of a stale flavor-causing substancefrom the spent grains in the sparging step for the second wort issuppressed. A more specific example is a process in which the extractretained by the spent grains is washed out under the acidic conditionusing hot water containing calcium salts and organic acids as hot waterfor the sparging, whereby a stale flavor-causing substance is lesseluted. The calcium salts may be any salt as long as it can form calciumphosphate as a result of the reaction with phosphate ion in wort. Theexamples include calcium chloride, calcium sulfate, calcium bicarbonate,and the like. Alternatively, instead of the above mentioned calciumsalts, other metallic salt can also be used as long as it can form aninsoluble phosphate salt through the reaction with phosphate ion in thewort with a degree of not affecting the beverage quality. Preferableorganic acids to be used along with the calcium salts are lactic acid,tartaric acid, acetic acid, and the like. Use of hot water comprisingcalcium salts and organic acids results in the formation of calciumphosphate, and decreasing the buffer action of wort. This means that thesparging can be carried out under the acidic condition depending onaddition of a small quantity of organic acid. Although it depends on theamount of calcium salt added, the preferable pH range under the acidiccondition is pH 5 or under for the hot water pH for preparation of thesecond wort.

[0017] As an alternative process to suppress the elution of a staleflavor-causing substance from the spent grains in the sparging step forthe second wort, a process is exemplified in which hot water for thesparging which can lower the temperature in the spent grains layerdraining off the first wort to 70° C. or under is used. This hot waterfor the sparging, which can lower the temperature in the spent grainslayer to 70° C. or under, can be acidified in advance as describedabove, for example, by being supplemented with calcium salts and organicacids. Such hot water for the sparging for lowering the temperatureand/or for the acidification will be used as sparge water from the upperpart of the spent grains in case of a lauter type filtering equipmentand as sparge water after the pressing-filtration in case of a mashfilter type filtering equipment.

[0018] An alternative process to restrict the carry-over of a staleflavor-causing substance into the second wort as described above can beexemplified by a process to control the supply of hot water for thesparging so that the sparging is completed with sugar content of thesecond wort run-off not ranging below 3° p. As mentioned above, sugarcontent of the wort run-off in the sparging step gradually decreases ingeneral in proportion to the increase in the sparge water amount. NPcontent in the second wort run-off, however, is kept at a high levelwithout correlating to the decrease in sugar content, meaning that thecarry-over of NP component into the second wort can be restricted bycompleting the sparging in a shorter duration, although the recovery ofsugar in the sparging decreases.

[0019] Further, as an alternative process to suppress the elution of astale flavor-causing substance into the second wort, a method can beexemplified in which the second wort is re-used during mashing process.This process of re-using the second wort during mashing process can beapplied in any appropriate manner such as by adding the second wort tomashing-in liquor, to mashing-in liquor for adjuncts treatment, to mashduring mashing, and the like. Other than these, the process can beapplied in a manner where mashing-in water is partially replaced withthe second wort. Although the second wort can be used in an appropriateamount which is obtained in an appropriate stage of the filtering stepfor the sparging, usually it is preferable to use a certain amount ofwort obtained at the final stage of the sparging. This process is basedon the following findings: NP content in the wort run-off holds arelatively high level, however, when the second wort containing NP, suchas the mashing-in water replaced and added with the second wort, is usedfor the mashing, and then the wort is separated from the spent grains bylautering, there is no increase in the NP content in the wort,indicating that a treatment with the suppression of the NP componentelution is achieved as a consequence. For example, it is set to remove apart of the second wort and the remaining second wort is combined withthe first wort to obtain the wort in which NP content is reduced byapproximately 1 ppb or more in terms of sugar content 11° p, whereas theremoved second wort can be used as a replacement in the subsequent oreven further mashing-in liquor.

[0020] There is no particular limitation as to a treatment process forremoving or reducing a stale flavor-causing substance in the second wortas described above, and any process such as adsorption, filtration,coagulation, and the like can be applied to the removal or reduction ofNP component in the second wort. One specific example is a process inwhich a part or a whole of the second wort is made to contact theactivated carbon and have its NP component adsorbed thereto so that NPcomponent is removed from or reduced in the wort. NP component can beremoved from or reduced in the wort by applying the wort to theactivated carbon column for the passage when the activated carbon is inthe form of particle or powder, and simply by filtering when it is inthe form of a panel.

[0021] The fermented malt beverages of the present invention such asbeer and the like, in which a stale flavor generation is suppressed,will not be specified in particular as long as it is obtained byfermenting the wort produced by the process for producing wort forfermented malt beverages as described above in details. The specificexamples include: a fermented malt beverage produced from wort forfermented malt beverages prepared with the second wort in which thecontent of a stale flavor-causing substance is reduced, being obtainedthrough the reducing treatment of a stale flavor-causing substance inthe second wort, with NP as an indicator for example; a fermented maltbeverage produced by fermenting wort in which NP content in the wholewort from mash separation process is reduced at least by 1 ppb in termsof sugar content 11° p; a fermented malt beverage produced from wort forfermented malt beverages prepared with the second wort obtained by atreatment to suppress the elution of a stale flavor-causing substancefrom spent grains such as an elution treatment using hot water for thesparging which contains calcium salts and organic acids, and such as anelution treatment using hot water for the sparging which can lower thetemperature in the spent grains to 70° C. or under; a fermented maltbeverage produced from wort for fermented malt beverages prepared withthe second wort obtained by a treatment to control the supply of hotwater for the sparging so that the sparging is completed with sugarcontent of the second wort not ranging below 3° p; a fermented maltbeverage produced from wort for fermented malt beverages prepared withthe second wort obtained by performing an adsorptive removal treatmentor a reducing treatment in which a part or a whole of the second wort ismade to contact the activated carbon; and so on.

[0022] The present invention will be explained more specifically withreference to the following examples, but these examples will not limitthe scope of the invention. Further, determination of NP contents in thefollowing examples was carried out as follows: wort was added to 0.2 Macetate buffer, pH of which was adjusted to 4.0 with acetic acid andsodium acetate, with the amount of one fifth of the buffer; the buffercontainer was capped and the buffer with the wort was then heat-treatedfor two hours at 100° C., which was then cooled down to roomtemperature; trans-2-nonenal was extracted by a solid-phase extractionusing a C18 cartridge, a Sep-Pak product, according to the method ofVerhagen et al. (J. Chromatgr., 393 (1987) 85-96); trans-2-nonenal wasthen turned to a derivative by dansyl hydrazine; and the trans-2-nonenalwas analyzed by HPLC (“HP1100”; Hewlett-Packard) employing a columnswitching method. In performing a column switching method, a 100×4.6 mmanalytical column (“ODS-AM”; YMC-Pack) and a 250×4.6 mm analyticalcolumn (“ODS-AM”, YMC-Pack) were used at a flow rate of 1.0 ml/min and0.85 ml/min, respectively.

EXAMPLE 1 Time-Course Change of Sugar Content and NP in the MashSeparation

[0023] 300 ml hot water was added to 100 g malt (malt:hot water=1:3) andthe mixture was mashed at the temperature program of 30 min. at 50° C.,60 min. at 65° C. and 10 min. at 78° C. The resulting mash was filteredthrough a funnel using a filter paper (“#2”, Toyo Roshi). After thefiltration, hot water was sparged on the spent grains six differenttimes, 70 ml each and the total of 420 ml. Sugar content and NP of eachof the filtered liquids (the second wort run-off) were determined. Sugarcontent (° p) was calculated by measuring the specific gravity and froma conversion table. FIG. 1 shows the results. Likewise, the mash wasfiltered in a lauter tun in the KL level pilot plant, and sugar contentand NP of the wort run-off were determined in time-course. The resultsare found in FIG. 2. The results shown in FIGS. 1 and 2 showed the factthat the decrease in NP was relatively smaller compared to the decreasein sugar content in the sparging. FIG. 2 particularly indicated that NPholds a high level without correlating to the decrease in sugar content,although sugar content in the wort is gradually decreased in general inproportion to the increase in the filtered liquid amount. These figuresalso show that no difference was observed between the NP contents in thefirst and second worts. These results together reveal that NP was elutedfrom the spent grains.

EXAMPLE 2 Reduced Amount of NP in the Whole Wort that is Effective forthe Trans-2-Nonenal Reduction in Beer

[0024] The first wort and second wort were combined and two types ofworts were prepared with different NP contents of 6.7 ppb and 7.4 ppbwith the same sugar content of 11° p. Hops were added to the worts andthe worts were then boiled. After the worts were cooled down, yeast wasadded to these two types of worts for fermentation and beer wasprepared. After the bottling, they were stored for four days at 37° C.,which were then determined for their trans-2-nonenal and a sensory testwas performed at the same time. The trans-2-nonenal level in beer wasproved to be 0.16 ppb from the wort of 6.7 ppb NP content and 0.19 ppbfrom the wort of 7.4 ppb NP content. The beer from the wort of 7.4 ppbNP content apparently released stronger stale flavor (cardboard flavor)in the sensory test. This result demonstrated that trans-2-nonenal levelin beer can be decreased significantly when NP in the whole wort isdecreased by about 1 ppb, thereby the generation of a stale flavor inbeer is suppressed.

EXAMPLE 3 NP Reduction by Sparge Hot Water with Lower Temperature

[0025] 300 ml hot water was added to 100 g malt (malt:hot water=1:3) andthe mixture was mashed for 30 min. at 50° C., 60 min. at 65° C. and 10min. at 78° C. Subsequently, hot water of 78° C. (experimental) and 100°C. (control) were aspersed five different times respectively, 100 mleach using a filter tube consisting of a thermal funnel. Then sugarcontent, pH and NP content in the whole worts were determined. Inaddition, the temperature in the spent grains layers in the mid-courseof the sparging were 70° C. (experimental) and 80° C. (control),respectively. The results are shown in Table 1. Table 1 demonstratesthat NP in the wort can be reduced by lowering the temperature of spargehot water and thereby lowering the temperature in the spent grains.TABLE 1 Temperature of NP sparge hot water NP The whole wort(temperature in Sugar The whole in terms of the spent grains contentwort 11° p during filtration) (° p) pH (NPppb) (NPppb) 100° C. (80° C.)10.63 5.85 9.4 9.7  78° C. (70° C.) 10.09 5.86 7.8 8.5

EXAMPLE 4 Reduction of NP by a Water Treatment of Sparge Hot Water

[0026] 300 ml hot water was added to 100 g malt (malt:hot water=1:3) andthe mixture was mashed for 30 min. at 50° C., 60 min. at 65° C. and 10min. at 78° C., followed by filtration. Then hot water, which wastreated with calcium chloride and lactic acid under the conditionindicated in Table 2, was aspersed five different times, 100 ml each toobtain the filtered wort. The case using hot water without addition ofthe calcium chloride and the lactic acid served as the control. Table 3shows the results. As shown in Table 3, NP in the wort can be reduced byperforming filtration with sparge hot water treated with calcium saltsand organic acids. TABLE 2 Lactic acid CaCl₂ (g/l) (g/l) pH Control 0 0Test 1 0.40 0.24 3.16 Test 2 1.00 0.60 2.93

[0027] TABLE 3 NP Sugar NP The whole wort content The whole wort interms of 11° p (° p) pH (NPppb) (NPppb) Control 10.09 5.86 8.1 8.8 Test1 10.13 5.67 6.7 7.3 Test 2 10.16 5.36 6.2 6.7

EXAMPLE 5 Replacement Addition of the Second Wort to Mashing-In Liquor

[0028] 300 ml hot water was added to 100 g malt (malt:hot water=1:3) andthe mixture was mashed for 30 min. at 50° C., 60 min. at 65° C. and 10min. at 78° C. After the first wort has run off, 350 ml hot water intotal was sparged three different times, 100 ml, 100 ml and 150 ml,respectively. The last 150 ml was collected for the replacement additionin the subsequent mashing-in liquor.

[0029] The second wort collected for the replacement addition in themashing-in liquor as described above had sugar content of 6.95° p and NPof 6.40 ppb. This second wort was added to the mashing-in liquor toreplace by 20%. Then 300 ml of this hot water with replacement additionwas added to 100 g malt (malt: hot water with replacement addition=1:3)and the mixture was mashed for 30 min. at 50° C., 60 min. at 65° C. andfor 10 min. at 78° C. After the filtration for the first wortseparation, 100° C. sparge hot water of 300 ml total was sparged threedifferent times, 100 ml each. The results are shown in Table 4. TABLE 4NP Sugar NP The whole wort content The whole wort in terms of 11° p (°p) pH (NPppb) (NPppb) Mashing-in liquor 13.39 5.87 8.07 6.7 with 20%replacement addition Mashing-in liquor 13.22 5.87 7.95 6.5 with normalwater

[0030] The above results show that the resulting NP level in the wortwas scarcely increased as opposed to the presumption that it would beincreased in accordance with the amount of the second wort replaced withthe mashing-in liquor when the second wort is partly used therein. Thisindicates that NP level will not be increased by the addition of thecollected second wort to the subsequent brew, therefore, the combineduse of the second wort, except the amount removed for the replacement,and the first wort as the filtered wort will lead to the suppression ofa stale flavor as a consequence.

EXAMPLE 6 Reduction of NP by the Treatment of the Second Wort with theActivated Carbon

[0031] 300 ml hot water was added to 100 g malt (malt:hot water=1:3) andthe mixture was mashed for 30 min. at 50° C., 60 min. at 65° C. and 10min. at 78° C. It was then filtered for the first wort separation.Subsequently, 300 ml hot water was sparged and only the second wort wascollected. The activated carbon was added to 200 ml each of the secondwort to the levels of 1000 ppm and 2000 ppm, which was then stirred fortwo minutes and filtered. NP levels in the filtered worts weredetermined. The results are found in Table 5. Table 5 demonstrates thatNP levels were considerably decreased by the addition of the activatedcarbon, while the sugar contents showed little decrease. TABLE 5 SugarTotal NP in terms content nitrogen NP of 11° p (° p) pH (mg/100 ml)(NPppb) (NPppb) Control 7.85 6.04 76.4 6.17 8.65 1000 ppm 7.79 6.02 71.80.93 1.31 added group 2000 ppm 7.74 6.03 66.9 0.47 0.67 added group

INDUSTRIAL APPLICABILITY

[0032] The present invention makes it possible to obtain the second wortwith the reduced content of a stale flavor-causing substance. By the useof this second wort with reduced content of a stale flavor-causingsubstance, fermented malt beverages such as beer and the like, in whichgeneration of a stale flavor is suppressed, can be produced.

1. A process for producing wort for fermented malt beverages wherein areducing treatment is performed for a stale flavor-causing substance inthe second wort in the mash separation process in course of theproduction of fermented malt beverages, to obtain the second wort withreduced content of a stale flavor-causing substance.
 2. The process forproducing wort for fermented malt beverages according to claim 1,wherein the reducing treatment of a stale flavor-causing substance isperformed with the trans-2-nonenal potential as an indicator.
 3. Theprocess for producing wort for fermented malt beverages according toclaim 2, wherein the reducing treatment of a stale flavor-causingsubstance in the second wort is performed so that the trans-2-nonenalpotential in the whole wort from mash separation process is reduced byat least 1 ppb in terms of sugar content 11° p.
 4. The process forproducing wort for fermented malt beverages according to any one ofclaims 1-3, wherein the reducing treatment of a stale flavor-causingsubstance is a suppressing treatment of the elution of a staleflavor-causing substance from the spent grains into the second wort insparging step which is a treatment to restrict the carry-over of a staleflavor-causing substance into the second wort.
 5. The process forproducing wort for fermented malt beverages according to claim 4,wherein the treatment to restrict the carry-over of a staleflavor-causing substance into the second wort is a treatment to suppressthe elution of a stale flavor-causing substance from the spent grainsinto the second wort in sparging step.
 6. The process for producing wortfor fermented malt beverages according to claim 5, wherein the treatmentto suppress the elution of a stale flavor-causing substance is atreatment using hot water for the sparging which contains calcium saltsand organic acids.
 7. The process for producing wort for fermented maltbeverages according to claim 5, wherein the treatment to suppress theelution of a stale flavor-causing substance is a treatment using hotwater for the sparging which can lower the temperature in the spentgrains layer to 70° C. or under.
 8. The process for producing wort forfermented malt beverages according to claim 4, wherein the treatment torestrict the carry-over of a stale flavor-causing substance into thesecond wort is a treatment to control the supply of hot water for thesparging so that the sparging is completed with sugar content of thesecond wort not ranging below 3° p.
 9. The process for producing wortfor fermented malt beverages according to claim 4, wherein the treatmentto restrict the carry-over of a stale flavor-causing substance into thesecond wort is a treatment to restrict the elution of a staleflavor-causing substance by using the second wort again during mashingprocess.
 10. The process for producing wort for fermented malt beveragesaccording to claim 9, wherein the elution of a stale flavor-causingsubstance is restricted by using mashing-in water, a part of which isreplaced with the second wort.
 11. The process for producing wort forfermented malt beverages according to any one of claims 1-3, wherein thereducing treatment of a stale flavor-causing substance is a removing orreducing treatment of a stale flavor-causing substance in the secondwort.
 12. The process for producing wort for fermented malt beveragesaccording to claim 11, wherein the removing or reducing treatment of astale flavor-causing substance in the second wort is a removing orreducing treatment in which a part or a whole of the second wort is madeto contact the activated carbon.
 13. A fermented malt beverage withsuppressed generation of a stale flavor which is obtained through thefermentation step from the wort produced by the process for producingwort for fermented malt beverages according to any one of claims 1-12.